Author Topic: K8 Engine Damage - cam shaft sprocket in pieces (Read 9309 times)

anotherCB · « **Reply #75 on:** August 17, 2020, 07:29:26 AM »

Great advice, thanks! I’ll be extra careful. Too much $$$ and time already in this (unplanned) rebuild, I can’t afford another “accident”!

ekpent · « **Reply #76 on:** August 18, 2020, 05:54:58 AM »

Good job on sticking to the project and keeping it moving along ! Don't forget that there are 4 small o-rings under the cam towers,two around the jets and 2 in the round recess in the head at each end for a blind hole. Sure you will put loctite on those two cam sprocket bolts. Here's hoping your riding soon.

anotherCB · « **Reply #77 on:** August 18, 2020, 06:27:13 AM »

Thanks for the reminder. I am pretty sure I marked all my locations where an o-ring needs to go, but I’ll quadruple check.
Expecting crank bearing shells in the mail tomorrow, have the plastic Auge already, so if all goes well and I don’t have to reorder different shells, the bottom end should go together this weekend.
Still need to lap the valves, started with a compound that I think was too coarse, so ordered a finer one.
I’ll keep y’all in the loop. Thanks for all the comments.

anotherCB · « **Reply #78 on:** August 18, 2020, 06:29:58 AM »

Oh and definitely “yes” on the loctite!

anotherCB · « **Reply #79 on:** August 20, 2020, 10:47:21 AM »

Progress is being made! Crank bearing shells came in, clearance is spot on (checked with Plastigage), test fitted both half’s together. Now I need to triple check that I have the dowels, crank seal, oil gallery oring and whatever else in place, clean the surfaces one more time and Hondabond it together.
Also the less coarse valve grinding paste arrived so I can tackle that next.

anotherCB · « **Reply #80 on:** August 21, 2020, 08:35:52 PM »

Will put pistons in tomorrow. From what I see in 95% of the comments is that the shiny ring goes on top, is that correct? Markings should face up for those rings I believe?
What about the oil rings, are they both identical? Can they be put in either way?
Thanks!

PeWe · « **Reply #81 on:** August 21, 2020, 10:05:36 PM »

http://forums.sohc4.net/index.php/topic,151435.msg1730443.html#msg1730443

anotherCB · « **Reply #82 on:** August 22, 2020, 07:03:15 AM »

Thanks, good post but I didn’t see in there which ring goes to the top. I’ll go with the shiny one since that seems to be what most posts say.

bryanj · « **Reply #83 on:** August 22, 2020, 07:55:27 AM »

Yes shiny top, black second all writing facing up.
Scraper ring expander first the one rail either side, dont matter which way up or which side of expander IF you are using new rings, if using old rings and you didnt keep bits in order-------go buy new rings

PeWe · « **Reply #84 on:** August 22, 2020, 12:10:55 PM »

Ring gaps checked in bores and OK?
Not too tight.

anotherCB · « **Reply #85 on:** August 22, 2020, 05:47:19 PM »

How tight is too tight? I followed the Clymer which only says “rings are usable when gap is less than 0.7 mm” which mine obviously is since I have new rings.
There is no mention of a minimum gap in the Clymer that I shouldn’t be under. I think I am at 0.2 or 0.15 but I didn’t measure it since I was way under 0.7 mm and thought that was all I needed to look at.
Edit: Found in the factory manual that end gap should be 0.2-0.4 mm
I haven’t bolted the cylinder down yet, so I could take it off and measure, what should I do?

PeWe · « **Reply #86 on:** August 22, 2020, 10:40:23 PM »

If ring gaps are too tight, pistons and bores will ruin when engine is hot, rings expands.

You can download the Honda workshop manual on this site.
http://manuals.sohc4.net/cb750k/

Top and 2nd ring 0.2-0.4mm
Oil rings 0.1-0.3mm.

All rings to be tested in each bore. Use the naked piston to press it straight into the bore where rings moves.

If too tight, file ends from out to in only. Flat needle file.
Small fine file clamped in a vise, hold the ring and squeeze and move one way only while pressed together and file, from out to in.

Many rings have sharp burrs that must be deburred.
My Wiseco rings on my JE pistons had a lot of that.

The last set of cheap Cruzinimage 61.5mm pistons had really tight gaps needed to file to OK gap.

But your pistons are not new?
This is for new pistons only that also need to be deburred on all sharp edges.

Old pistons check gap to avoid too large gap, leaking compression one wat, oil the other.
This can also indicate worn bores, too large bore/piston clearance and will smoke.

anotherCB · « **Reply #87 on:** August 23, 2020, 06:19:27 AM »

Thanks for the detailed info PeWe. Luckily I haven’t bolted things down yet, so I’ll take the cylinders off and check to be safe.
The engine only had 15k miles on it and I reused the pistons. I measured gaps between rings and landings and they were tight, definitely below the max tolerance.
The pistons themselves also measured within spec, I don’t have an inside micrometer so couldn’t measure the bore but I would be surprised if it was worn too much. Have it a good hone and it looked good.

Just out of curiosity, What’s the easier way to install pistons? Install them all on the connection rods first and then in the cylinder (that’s how I did it) or is it easier to install them one by one in the cylinders first and then hook them up to the con rods?

Thanks again and happy Sunday (wrenching)!

PeWe · « **Reply #88 on:** August 23, 2020, 07:21:32 AM »

If rings have been used before on pistons running in the bores without marks after running really warm probably OK.

All pistons on rods, rotate crank so 2-3 goes first. Block them with wood under so crank will not move...

anotherCB · « **Reply #89 on:** August 23, 2020, 09:31:40 AM »

Rings are new. I will pull the bottom of and mesasure to be safe. Nothing bolted down yet so not too bad.

anotherCB · « **Reply #90 on:** August 23, 2020, 04:06:06 PM »

Pulled the cylinders off and measured all rings in three different positions in the bore, all between 30 and 40/100 mm and no bore has more than 5/100 mm difference between top, Center and bottom, so this looks good.
I have the tiniest gap between rings and ring landings, something like 4/100 mm (yes 4/100, not 0.4 😏). Rings move easily in their groves so I assume that’s fine?
Also is it recommended to use gasket sealant together with the gasket at the bottom end?
Thanks!

robvangulik · « **Reply #91 on:** August 23, 2020, 04:16:37 PM »

Quote

Also is it recommended to use gasket sealant together with the gasket at the bottom end?

NO,NEVER!

PeWe · « **Reply #92 on:** August 24, 2020, 12:40:29 AM »

No sealant needed.
Except for:
- Under rubber pucks under cam holders.
- Around rubber grommet holding wires on alternator cover.
- Between cases.

Note! Only thin layers.

If valve cover leaks it might need to be grinded flat. Grit 240 until flat, 400 final.
Edit: 2 x A4 sized papers glued on a truly flat surface.

I have used a very thin layer of sealer on the oil seal making it sticky, outgoing shaft/final gear.

bryanj · « **Reply #93 on:** August 24, 2020, 01:53:48 AM »

If you are really worried about gasket sticking, moving or ripping you can put clean greas either side, obviously NOT the head gasket though!

anotherCB · « **Reply #94 on:** August 24, 2020, 08:03:06 AM »

Thanks everyone, taking notes!

Damaged a valve stem seal yesterday when reinstalling valves in the head, which means it will be another 7 days at least until I get the engine together. Maybe not too bad, so I can take it slowly!

PeWe · « **Reply #95 on:** August 24, 2020, 09:04:04 AM »

Those seals good to have extra of.

anotherCB · « **Reply #96 on:** August 24, 2020, 12:53:27 PM »

Quote from: PeWe on August 24, 2020, 09:04:04 AM

Those seals good to have extra of.

Agree. They came in my gasket set and they didn't put one extra in

Well, more time for me to read up on stuff while waiting on the one shaft seal!

Remcod · « **Reply #97 on:** August 24, 2020, 01:13:29 PM »

Check hondaman post on the thickness of the 2 o-rings between head and cilinder not being correct in aftermarket gasket sets causing leaks. Get the correct ones 2.67x10.77

anotherCB · « **Reply #98 on:** August 24, 2020, 02:36:50 PM »

Quote from: Remcod on August 24, 2020, 01:13:29 PM

Check hondaman post on the thickness of the 2 o-rings between head and cilinder not being correct in aftermarket gasket sets causing leaks. Get the correct ones 2.67x10.77

Thanks for bringing it up, it matters even more because I am using the MLS head gasket it seems. Will definitely look into this.

PeWe · « **Reply #99 on:** August 24, 2020, 10:29:21 PM »

MLS head gasket does not need o-rings.
I used 2 for oil feed just for sure, but not thicker.

Too thick o-rings can collapse blocking the hole. This has been up on decked cylinders.

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Author Topic: K8 Engine Damage - cam shaft sprocket in pieces (Read 9309 times)